Joints of this type should exhibit a certain number of qualities that are hard to reconcile in practice.
The joints should be able to support very great pressures between the inside wall and outside wall of the pipe string. They should also exhibit a mechanical resistance comparable to that of the pipe elements they are to join.
Considering that the pipe string equipped with these joints is intended to be place in deep boreholes, it is desirable that the diameter of the joint exceed the pipe diameter by the smallest possible value.
These joints must also exhibit a reliable fluid tightness, even after repeated screwings and unscrewings, a given male end being able to be mounted on this occasion on different female ends, despite fabrication tolerances that are inherent in all industrial production.
It is also desirable that the joint to the greatest extent possible assure self-repair of fluid-tight surfaces, because these latter are relatively often subjected to deteriorations during on-site handling.
The joint according to the invention is of the type wherein the ends of two males elements are joined by a female sleeve, each male element being provided with a truncated conical threading that engages in a corresponding female threading made in the sleeve.